1. Field of the Invention
The present invention relates to a filter for a display apparatus and a display apparatus having the same, and more particularly, to a filter for a display apparatus and a display apparatus having the same, which includes an external light-shielding layer preventing occurrence of ghosting using a difference between refractive indexes of a base substrate and an external light-shielding part.
2. Description of Related Art
A PDP apparatus generates a gas discharge between electrodes by a direct current (DC) voltage or an alternating current (AC) voltage which are supplied to electrodes. Here, ultraviolet light is generated. Then, a phosphor is exited by ultraviolet light, thereby emitting light.
However, the PDP apparatus has a defect in that an amount of emitted electromagnetic (EM) radiation and near infrared (NI) radiation with respect to a driving characteristic is great, surface reflectivity of the phosphor is great, and color purity due to orange light emitted from helium (He), or xenon (Xe) used as a sealing gas is lower than the CRT.
Also, EM radiation and NI radiation generated in the PDP apparatus may have harmful effects on human bodies, and cause sensitive equipment such as wireless telephones, remote controls, and the like, to malfunction. Therefore, in order to use the PDP apparatus, it is required to prevent emission of EM radiation and NI radiation emitted from the PDP apparatus from increasing to more than a predetermined level. PDP filters having functions such as an EM radiation-shielding function, an NI radiation-shielding function, a surface antiglare function, enhancement of color purity function, and the like, are used for EM radiation-shielding and NI radiation-shielding while simultaneously reducing reflected light, and enhancing color purity.
The PDP apparatus is made of a panel assembly including a discharge space where a gas discharge phenomenon occurs, and a PDP filter for EM radiation-shielding and NI radiation-shielding. Since the PDP filter is equipped in a front unit of the panel assembly, transparency is required to simultaneously emit light and perform shielding functions.
External light may enter the panel assembly passing through the PDP filter in a condition that an outer surface is bright, that is, in a bright room condition with the PDP apparatus according to the conventional art. Accordingly, an overlapping between incident light generated in the discharge space of the panel assembly, and the external light entered passing through the PDP filter from the outer surface occurs. Accordingly, a contrast ratio decreases in the bright room condition, and therefore screen display capacity of the PDP apparatus is deteriorated. Therefore, there is a need for a PDP filter including an external light-shielding layer filled with an absorption material to absorb external light.
In a conventional external light-shielding layer for improving contrast ratio, in order to minimize loss of a display light source and at the same time shield external light, the external light-shielding layer is designed such that a refractive index of an external light-shielding part is less than that of a base substrate of the external light-shielding layer, so that a part of light emitted from a display is totally reflected and transmitted, and thus, remarkably reducing loss of the light emitted from the display using the external light-shielding part.
However, in the conventional art, in order to improve transmittance of the light emitted from the display, a refractive index of the external light-shielding part must be reduced to 0.01 or less than that of the base substrate. However, there arises a problem in that an image is distorted due to occurrence of ghosting by a difference between reflective indexes of the light emitted from the display and the light totally reflected and transmitted.